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A Synthetic Bandwidth Method for High-Resolution SAR Based on PGA in the Range Dimension.

Li J, Chen J, Liu W, Wang P, Li C - Sensors (Basel) (2015)

Bottom Line: The synthetic bandwidth technique is an effective method to achieve ultra-high range resolution in an SAR system.Furthermore, an improved cut-paste method is proposed to combine the signals in the frequency domain.Imaging results based on both simulated and real data are presented to validate the proposed approach.

View Article: PubMed Central - PubMed

Affiliation: School of Electronic and Information Engineering, Beihang University, Beijing 100191, China. lijincheng_buaa@163.com.

ABSTRACT
The synthetic bandwidth technique is an effective method to achieve ultra-high range resolution in an SAR system. There are mainly two challenges in its implementation. The first one is the estimation and compensation of system errors, such as the timing deviation and the amplitude-phase error. Due to precision limitation of the radar instrument, construction of the sub-band signals becomes much more complicated with these errors. The second challenge lies in the combination method, that is how to fit the sub-band signals together into a much wider bandwidth. In this paper, a novel synthetic bandwidth approach is presented. It considers two main errors of the multi-sub-band SAR system and compensates them by a two-order PGA (phase gradient auto-focus)-based method, named TRPGA. Furthermore, an improved cut-paste method is proposed to combine the signals in the frequency domain. It exploits the redundancy of errors and requires only a limited amount of data in the azimuth direction for error estimation. Moreover, the up-sampling operation can be avoided in the combination process. Imaging results based on both simulated and real data are presented to validate the proposed approach.

No MeSH data available.


Schematic diagram of the cut-paste method.
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f7-sensors-15-15339: Schematic diagram of the cut-paste method.

Mentions: As for the combination operation, we propose an improved cut-paste method that combines the sub-band signals in the frequency domain, as shown in Figure 7. In this processing, the sub-band signals are up-sampled uniformly by putting the sub-spectrum data into the appropriate frequency point in the frequency domain, and the up-sampling operation can be avoided for the individual sub-band signals. Assume the frequency vectors of the combined signal and the sub-band signal are respectively Fτ and fτ (k), expressed as:(30)Fτ=[fc−N2fs,fc−N2fs+fsNbins,⋯,fc+N2fs](31)fτ(k)=[fc(k)−fs2,fc(k)−fs2+fsnbins,⋯,fc(k)+fs2]where nbins, Nbins is the corresponding number of sampling points of the sub-band signal and the combined signal. The conventional cut-paste method can only be used if each fτ (k) is the subset of Fτ, i.e., the sub-spectrum is a part of the reconstructed spectrum exactly. Otherwise, there is no appropriate position to paste the sub-band signals in the frequency domain. In this case, the system parameters, such as pulse length and A/Dsampling rate, are required to be adjusted [6]. This will increase system complexity, especially considering that many multi-sub-band systems are upgraded from the existing single band system. This problem can be solved through a phase multiplication operation. Let the frequency difference of the k-th sub-band be Δfτ (k). Then:(32)fτ(k)+Δfτ(k)⊆Fτ


A Synthetic Bandwidth Method for High-Resolution SAR Based on PGA in the Range Dimension.

Li J, Chen J, Liu W, Wang P, Li C - Sensors (Basel) (2015)

Schematic diagram of the cut-paste method.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4541834&req=5

f7-sensors-15-15339: Schematic diagram of the cut-paste method.
Mentions: As for the combination operation, we propose an improved cut-paste method that combines the sub-band signals in the frequency domain, as shown in Figure 7. In this processing, the sub-band signals are up-sampled uniformly by putting the sub-spectrum data into the appropriate frequency point in the frequency domain, and the up-sampling operation can be avoided for the individual sub-band signals. Assume the frequency vectors of the combined signal and the sub-band signal are respectively Fτ and fτ (k), expressed as:(30)Fτ=[fc−N2fs,fc−N2fs+fsNbins,⋯,fc+N2fs](31)fτ(k)=[fc(k)−fs2,fc(k)−fs2+fsnbins,⋯,fc(k)+fs2]where nbins, Nbins is the corresponding number of sampling points of the sub-band signal and the combined signal. The conventional cut-paste method can only be used if each fτ (k) is the subset of Fτ, i.e., the sub-spectrum is a part of the reconstructed spectrum exactly. Otherwise, there is no appropriate position to paste the sub-band signals in the frequency domain. In this case, the system parameters, such as pulse length and A/Dsampling rate, are required to be adjusted [6]. This will increase system complexity, especially considering that many multi-sub-band systems are upgraded from the existing single band system. This problem can be solved through a phase multiplication operation. Let the frequency difference of the k-th sub-band be Δfτ (k). Then:(32)fτ(k)+Δfτ(k)⊆Fτ

Bottom Line: The synthetic bandwidth technique is an effective method to achieve ultra-high range resolution in an SAR system.Furthermore, an improved cut-paste method is proposed to combine the signals in the frequency domain.Imaging results based on both simulated and real data are presented to validate the proposed approach.

View Article: PubMed Central - PubMed

Affiliation: School of Electronic and Information Engineering, Beihang University, Beijing 100191, China. lijincheng_buaa@163.com.

ABSTRACT
The synthetic bandwidth technique is an effective method to achieve ultra-high range resolution in an SAR system. There are mainly two challenges in its implementation. The first one is the estimation and compensation of system errors, such as the timing deviation and the amplitude-phase error. Due to precision limitation of the radar instrument, construction of the sub-band signals becomes much more complicated with these errors. The second challenge lies in the combination method, that is how to fit the sub-band signals together into a much wider bandwidth. In this paper, a novel synthetic bandwidth approach is presented. It considers two main errors of the multi-sub-band SAR system and compensates them by a two-order PGA (phase gradient auto-focus)-based method, named TRPGA. Furthermore, an improved cut-paste method is proposed to combine the signals in the frequency domain. It exploits the redundancy of errors and requires only a limited amount of data in the azimuth direction for error estimation. Moreover, the up-sampling operation can be avoided in the combination process. Imaging results based on both simulated and real data are presented to validate the proposed approach.

No MeSH data available.